Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.85	13.246%	$247.8389	$247.84	$247.85	$247.80
Purchase #2	$169.34	13.352%	$191.9503	$191.95	$191.95	$192.00
Purchase #3	$124.87	13.193%	$141.3441	$141.34	$141.35	$141.30
Purchase #4	$71.85	9.739%	$78.8475	$78.85	$78.85	$78.80
Purchase #5	$103.96	12.630%	$117.0901	$117.09	$117.10	$117.10
Purchase #6	$124.89	13.687%	$141.9837	$141.98	$142.00	$142.00
Purchase #7	$245.94	4.268%	$256.4367	$256.44	$256.45	$256.40
7 purchase totals =	$1,059.70		$1,175.4913	$1,175.49	$1,175.55	$1,175.40